In an article entitled: "Charge-Coupled Devices -- A New Approach to MIS Device Structure", IEEE Spectrum, July 1971, pp 18-27, W. S. Boyle and G. E. Smith describe a new information-handling structure, the charge-coupled device, (CCD). The device stores a minority-carrier charge in potential wells created at the surface of a semiconductor and transports the charge along the surface by the application of bias potentials to control electrodes so as to move the potential wells.
Numerous applications have been proposed for the CCD. It can be utilized as a transversal filter, such as described in an article by A. Ibrahim et al entitled: "Multiple Filter Characteristics Using a Single CCD Structure", International Conference on the Application of Charge-Coupled Devices, October, pp 245-249; or as a recursive filter, such as described in an article by D. A. Sealer and M. F. Tompsett entitled: "A Dual Differential Analog CCD For Time-Shared Recursive Filters", ISSCC February 1975, pp 152-153. One disadvantage of prior structures of this type is that in order to provide both positive and negative coefficients of the sampled signals, it is necessary to subtract two charge signals at each delay stage. This is generally achieved utilizing a differential amplifier. However, the success of this approach requires the integration of a MOST (metal-oxide-silicon-transistor) operational amplifier on the same chip as the CCD, to reduce the final cost.